This invention relates to roller assemblies for guiding panels, such as doors and the like, slidably along a railed track. More particularly, it is directed to such assemblies incorporating new and improved means for preventing roller derailment.
It is conventional to mount a sliding door in a door frame or opening having a railed track facing and parallel to the bottom edge of the door, and to provide in the bottom edge portion of the door two or more grooved rollers for riding on the rail of the track to guide the door in smooth sliding movement along the track. Advantageously, the rollers are fabricated of a relatively, low-friction material such as nylon. In one known form of construction, described for example in U.S. Pat. No. 4,064,592, each roller is rotatably mounted in a U-shaped housing member which is itself pivotally carried by an outer housing or bracket mounted in the door, so that the angular position of the U-shaped member relative to the outer housing can be adjusted (to locate the roller at the proper height for a particular installation) by means of an adjusting screw carried in the outer housing and bearing against the U-shaped member.
Roller-mounted sliding doors are susceptible to lateral displacement or derailment, e.g. under conditions of severe wind loading such as may be encountered during heavy storms, especially because the low-friction characteristics of the rollers (though desirable for smooth door movement) enable them to jump or slip quite easily off the track rails. Various expedients have accordingly heretofore been proposed to prevent derailment of sliding doors.
One such expedient involves the provision of vertical flanges on the tracks for engaging the bottom edge portions of the doors to retain the doors on the tracks. These flanges, however, constitute upwardly projecting obstacles which are hazardous to persons walking through the door openings, as well as being aesthetically unattractive and vulnerable to bending or other damage. In this regard, it may be mentioned that in a currently preferred track configuration, herein termed a "flat track," the track rail on which the rollers ride is recessed between parallel horizontal lands, thereby to protect the rail from damage, minimize hazards to walkers, and present a pleasingly unobtrusive appearance.
Since the track rail is commonly formed as an upstanding web having an enlarged lip or bead at the top for engagement by the rollers, it has also been proposed to provide derailment-inhibiting retainer elements that extend downwardly from the axle of and in overlapping relation to each roller (as described in the aforementioned U.S. Pat. No. 4,064,592, and in U.S. Pat. No. 3,033,285), or elsewhere along the bottom edge of the door (as described in U.S. Pat. No. 3,745,706), to hook under the rail lip or bead. The use of these devices tends to increase the difficulty of installing and especially of removing the doors to which they are attached; moreover, their ability to withstand door-displacing forces is limited, owing to the fact that they must be flexible in order to facilitate such installation and removal.
Additionally, elements mounted separately from the rollers along the bottom edge of a door, and having downwardly-opening grooves or notches for the rails, have been proposed and employed for retaining sliding doors on their tracks. An example of this type of device is a rigid metal lug adapted to be force-fitted into the lower end of a vertical stile of a sliding door. A structurally somewhat similar element is described in U.S. Pat. No. 3,085,298. Such devices must be individually mounted and positioned with considerable care, contributing to the complexity of door installation, and giving rise to the possibility that an installer in the field may inadvertently omit them, with the result that the installed door is unprotected against derailment.